The present invention relates to a safety tire, and more particularly to a pneumatic tire which enables the driver to drive the vehicle to the repair shop if the tire becomes deflated due to rupture or puncture by a nail or the like.
Conventionally, in order to maintain safety in the event of a tire puncture or burst, there have been proposed a pneumatic tire having an elastic support member therein, a pneumatic tire having a double bulkhead structure provided therein with an annular member having an independent airtight chamber, and a pneumatic tire having an elastic reinforcing layer disposed inside the sidewalls and/or shoulders of the tire.
The tires of the first two types are accompanied by an increase in weight, and, as compared with normally structured tires, are inferior in high speed driving performance and higher in manufacturing cost and are not economical, while the last type is not sufficient in its load supporting effect.
Accordingly, a radial tire having an aspect ratio of 60% or less, in which the tread width is wider than the maximum width of the carcass, and the tread edges are defined in a range smaller than the sectional height of the carcass, is proposed for a safety tire by the present applicant(s) through the specification and accompanying drawings of Japanese Patent Application No. 61-11320.
The safety tire of the previous proposal is intended to allow travel by a widened tread if the internal pressure drops suddenly due to puncture or the like, and therefore it is simple in structure and low in manufacturing cost and hence solves the problems of the prior art to a considerable degree prior to the present invention.
However, even in the tire of the prior art, the bend in the sidewall accompanied with a decrease in the sectional height of the tire caused by a drop in internal pressure, tends to become nonuniform, and the strength of the carcass may be lowered by such a bend.
It is therefore, an object of the present invention to provide a safety tire capable of solving the above-mentioned problems by setting the curvature shape of the carcass of the sidewalls, especially from the point of the maximum width to the bead, in a specified shape, so as to bend easily and uniformly when the internal pressure drops due to a puncture and to prevent damage in such bending zone.